Abstract
The gametogenesis and reproduction of the matrinxã, Brycon orthotaenia in the São Francisco river, Pirapora Region, Minas Gerais, were studied from December, 1998 to November, 1999. The matrinxã B. orthotaenia is an endemic species in the São Francisco river basin in Brazil and important for commercial fishing. The size of the 1st gonadal maturation, indicated by the total length of the smallest spent males and spawned female, was 32.0 and 40.5 cm respectively. Reproduction occurred from October to January, when high frequencies of females and males at an advanced ripening/mature stage and spawned females were found. The short spawning period and histological characteristics of spawned ovaries containing only oocytes in stages of initial development, along with post-ovulatory and atresic follicles, indicated that Brycon orthotaenia presents total spawning.
Highlights
Human population growth and an increase in agricultural and industrial activities, as well as dam construction, mineral extraction, deforestation and predatory fishing cause changes in the environment that directly affect fish
Morphology of ovaries and oogenesis The ovaries of B. orthotaenia were paired, elongated organs located in the coelomic cavity laterally to the digestive tube, ventrally to the kidneys and ventro-laterally to the gas bladder
Morphology of testes and spermatogenesis The testes of B. orthotaenia were paired, elongated and fusiform organs located in the coelomic cavity laterally to the digestive tube, ventrally to the kidneys and ventro-laterally to the gas bladder
Summary
Human population growth and an increase in agricultural and industrial activities, as well as dam construction, mineral extraction, deforestation and predatory fishing cause changes in the environment that directly affect fish. As a result of this environment degradation, the São Francisco river, which was one of the main fishing resources in Brazil, is presently a fishery in decline (Godinho & Godinho, 2003). Taking this into consideration, the matrinxã, Brycon orthotaenia (Günther, 1864) known previously as B. lundii Reinhardt, 1874, an endemic species in the São Francisco river basin and important for commercial fishing, reaching 7 kg of body weight, is threatened with extinction in some regions of the São Francisco basin (Sato, 1999). Establishing the reproduction period and length of gonadal maturation, using microscopic criterion justify implementing fishery legislation more accurately (Bazzoli, 2003).
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